package mutt found 618607 1.7.2-1+deb9 thanks I think I can reproduce this by using a davmail imap server (which gives easy control of the socket timeout). Disabling the socket timeout made for a much improved experience. The davmail version I used was 5.0.0.2801-2~bpo9+1.
My only non-default imap setting is set imap_keepalive = 120 The $timeout variable is set at default (600s) Regards Vince
